The present invention relates to water heating and delivery systems employing high wattage heating elements to effect rapid response water heating, and more particularly to an improved means for controlling activation and deactivation of the heating elements in such a rapid response system.
Rapid response water heating and delivery systems are typically utilized either as a replacement for existing hot water heaters having large tank capacities, or are connected in series with such existing hot water tanks at a point near a water delivery location such as a faucet to improve the overall energy efficiency of the system by enabling the large capacity tank to be set at a lower temperature, with the rapid response system acting as an auxiliary heater to deliver hot water at a desired use temperature at the delivery location only as needed. Typical applications of such rapid response systems include health care facilities, laboratories, photo processing labs, industrial wash stations, hotels and restaurants, residential uses, and as a backup for solar water heating systems.
Such rapid response water heating systems generally include high wattage heating elements operative to deliver large amounts of energy to water very quickly as it flows through the system to raise the water from an input temperature level to a desired output temperature. The operation of such rapid response systems requires that the activation and deactivation of the high wattage heating elements be closely controlled to avoid conditions wherein the elements are operating during times of reduced water flow through the system. More particularly, it is important to insure an adequate flow of water through such rapid response systems during operation of such heating elements to avoid burning out the heating elements and/or otherwise damaging the system. For this reason, such rapid response heating systems require means to sense water flow rates, as well as means to activate the heating elements only when desired flow rates exist to avoid overheating. Known means for effecting such control utilize flow sensing devices equipped with magnetic proximity switches for activating and deactivating the electrical system for delivering energy to the heating elements. However, it has been found that rapid response systems utilizing such flow sensing devices are disadvantageous and indeed have a limited life when utilized with water sources or environments having a high iron content. It is, therefore, desirable to provide a rapid response water heating and delivery system which possesses a life span which is unaffected by the type of water being heated or the iron content therein.
The present invention is intended to satisfy the above desirable features and objectives through the provision of a new and improved rapid response water heating and delivery system having a flow sensing and heater activating means which is unaffected by the type of water flowing through the system. The invention includes a flow restrictor which creates a pressure differential within the water inlet point to the heating system. At a predetermined input flow rate, the flow restrictor yields a threshold pressure differential that is sensed by a novel pressure differential switch, which in turn activates the electrical system for energizing the heating elements. Upon reduction of water flow through the system below the predetermined flow rate, the pressure switch will likewise operate to deactivate the electrical system. The pressure differential switch also can be adjusted to actuate the electrical system at different desired levels of flow in the system.
The above and other features of the invention will become apparent from a reading of the detailed description of the preferred embodiment, which makes reference to the following set of drawings.